Mining operations, including mining operations that remove bitumen from oil sands, generate a waste stream that may be referred to generally as mine tailings. These mine tailings often may include a significant quantity of water and may be stored in a storage facility, or structure, such as an enclosure, or pond. Over time, particles within the stored mine tailings may settle, producing a relatively stable suspension of the particles in the water that may have a solids content of approximately 30 wt %. This suspension may be referred to herein as mature fine tailings (MFT) and has a very low shear strength. Thus, the MFT cannot be built upon and vegetation often may not grow thereon.
Because of the long dewatering time for the MFT and the high rate at which mine tailings may be generated, large volumes of mine tailings have been, and continue to be, generated in various parts of the world. Environmental concerns, space constraints, and/or government regulations may dictate that these mine tailings be processed to a more stable form, thereby permitting reclamation of the storage facility, revegetation of the mine tailings, and/or beneficial use of the storage facility. As an illustrative, non-exclusive example, Canadian Directive 74 requires that stored mine tailings be processed such that they have a shear strength of at least 5 kilopascals (kPa) within one year of storage and a shear strength of at least 10 kPa within 5 years of storage. Meeting this directive, for example, may require dewatering of the stored mine tailings at a rate that is significantly higher than the dewatering rates that are experienced when the mine tailings are simply placed in the storage facility and allowed to dewater naturally.
Several technologies have been developed that may increase the dewatering rate of the stored mine tailings; however, these technologies often are costly to implement, require large amounts of space, and/or are ineffective at reaching a target shear strength within a desired period of time, such as to keep up with the rate at which additional mine tailings are being generated. As an illustrative, non-exclusive example, mine tailings may be flocculated to increase a solids content thereof and then spread in very thin layers to permit additional dewatering. However, the allowable thickness of the layers, the large volumes of mine tailings that may be generated, and the time needed to dewater each layer dictate that these sloped beaches must cover very large areas, thereby creating additional space constraints and/or environmental impacts. Thus, there exists a need for improved systems and methods for dewatering mine tailings.